State of the art for occupant classification and detection are foil based pressure sensor systems which are integrated in every single seat. The integration of foil sensors in each individual seat results in relatively high integration costs. Furthermore the wiring of the foil based pressure sensors causes problems especially in case of removable vehicle seats. Finally conventional foil based systems can only detect if people are sitting directly on the seat. Out-of-position cases (like sitting between two seats or sleeping on the rear bench) cannot be detected.
Radar based in-vehicle systems have not been established on the market due to high costs. In general each single seat needs a separate radar sensor.
On the other hand radar technology offers some advantages in comparison to other occupancy detection and classification methods. It is a contactless and invisible measurement system which can easily be integrated behind plastic covers and textiles. Radar systems can measure smallest motions within the range of micrometers. Existing state of the art solutions use a conventional single frequency Doppler radar as a motion sensor. This is not sufficient in order to get a reliable statement about the occupancy state and if the human is in or outside the car.